Electric insulator



Feb. 2, 1954 G. H. JONKER 2,668,118

ELECTRIC INSULATOR Filed Jan. 22, 1952 ENTOR Gerur inrich Jonker Patented Feb. 2, 1954 UNITED STATES 2,668,118 ELECTRIC INSULATOR Gerard Heinrich J onker, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application January 22, 1952, SerialNo. 267,591

Claims priority, application. Netherlands February 8, 1951' 7 Claims. (01. 106-39) The invention relates to ceramic electric insulators having a low temperature coefficient of the dielectric constant, more particularly for use as a capacitor dielectric.

Because titanium dioxide and variou titanates have a negative temperature coefficient of the dielectric constant and because most other oxide materials have a positive temperature coefficient, it has been suggested to combine titanium-dioxide or titanates with other oxides, such for example, as magnesium oxide, beryllium oxide, zirconium oxide, tin oxide and cerium ox-. ide, or oxide compounds, such for example, as zirconates and stannates, to act upon the temperature coefl'icient of ceramic dielectrics. Various of theseknown combinations have limitations in working, for example, a high sintering temperature or a short sintering period and with others the desired temperature coefficient is only obtained at low values of the dielectric constant. Consequently there is still a need for new means in the art to obtain the aforesaid result.

The invention relates to a ceramic insulator The products contain a compound ofthecom- 1 position ZrTiO which may b termed '-zirconiumtitanate, The zirconiumtitanate is a dielectrically very valuable compound which, how

ever, has a limitation in that in its pure state it can be sintered only with diiiiculty, The material according to the invention, which contains zirconiumtitanate, can, however, be sintered to compactness at temperatures between 1300 and 1500, in accordance with the zirconiumtitanate content. The temperature coefficientof the dielectric constant lies between -200.10- and 10.10 and the dielectric constant between approximately 30 and 45.

The compositions having a titaniumdioxide content of about50 mol. per cent have the ad-i vantage that the value of the dielectric constant (e) is at least 35, the temperature coefiicient and the tan 6 having low'values- Of some of these panying drawing by the numerals 1. to 5, the dielectric values and the sintering temperatures are indicated in the Table I:

Table I ZnO percent M01. percent Wt. percent Wt. percent wt. percent A shift of the temperature coeificient in positive sense, though attended with a slight reduc- 40 tion of the dielectric constant, may be obtained by replacing in the aforesaid compositions the titaniumoxide and the zirconiumoxide to such a portion by tin oxide that the tin oxide content of the material is at the most 30 mol. per cent. A few examples thereof are given in Table II.

Table II ZnO ZIO: T101 SnO:

Tg.6 Temp. Slut Mol. Wt. M01. Wt. Mol. Wt. Mol. Wt. f6, 9&3,- Temp.

perperperperperperperpercent cent cent cent cent cent cent cent compounds, which are indicated in the accom--.

The titaniumdioxide may furthermore be replaced to such a portion by aluminum oxide that the aluminumoxide content is at the most equal to the zinc oxide content and is maximum 15 mol. per cent. A few examples of such compositions are given in Table III.

Table III 4 drawing of the ternary system ZrO2ZnOTiO2.

3. A capacitor dielectric consisting of a sintered mass of about 1 to 40 mol. per cent of ZnO, more than 10 mol. per cent of ZrOz, about 33 mol. per cent plus of the Z102 content to 55 mol. per cent of T102, and up to 30 mol. per cent ZnO A120: ZrO: TiO:

. tans Temp. 8mm Mol. Wt. Mol. Wt. Mol. Wt. Mol. Wt. f6, @1 temp.

perperperperperperperpercent cent cent cent cent cent cent cent If desired, use may be made of sintering or fluxing agents in the manner known in ceramic art in order to reduce the sintering temperature. For this purpose use may, for example, be made of silicates, such as bentonite and fluorides, such as CaF2 and MgFa.

The manufacture of the dielectrics on the basis of zirconiumtitanate according to the invention may be carried out as follows. The oxides, compounds of these oxides or compounds converted into the former by heating are mixed in the aforesaid ratio, if necessary with the addition of a sintering agent and a combustible binder, for example by grinding in a ball mill. The mass is then heated; the temperature may be raised with a speed of, for example, 500 per hour to the sintering temperature; then heating is continued at this temperature for one hour and cooling is efiected in two hours.

For use in capacitors the insulators are preferably shaped in the form of tubes and provided with electrodes, for example by applying silver by burning.

What I claim is:

1. A capacitor dielectric consisting of a sintered mass of about 1 to 40 mol. per cent of ZnO, more than 10 mol. per cent of H02, and about 33 mol. per cent plus A; of the ZrOz content to 55 mol. per cent of T102, said product living wholly within a pentagon ABCDE shown in the accompanying drawing of the ternary system ZrOz-ZnO--Tl0z.

2. A capacitor dielectric consisting of a sintered mass of about 1 to 40 mol. per cent of ZnO, more than 10 mol. per cent of ZrO2, and about 50 mol. per cent of TiO2, said product lying wholly within a pentagon ABCDE shown in the accompanying of $1102 replacing a corresponding proportion f the 2102 and H02. l

4. A capacitor dielectric consisting of a sintered mass of about 1 to 40 mol. per cent of ZnO, more than 10 mol. per cent of ZrO2, about 33 mol. per cent plus /3 of the ZrOz content to 55 mol. per cent of TiO2, and up to about 15 mol.

6. A capacitor dielectric consisting of a sintered mass of about 1 to 40 mol. per cent of ZnO, more thanlO mol. per cent of ZI'Oz, about 33% mol. per cent plus of the ZrO2 content to 55 mol. per cent of Ti02, up to 30 mol. per cent of S1102 replacing a corresponding proportion of the ZIOz and Ti02 content and a fluxing agent.

'7. A capacitor dielectric consisting of a sin 1 tered mass of about 1 to 40 mol. percent of ZnO, more than 10 mol. per cent of ZlOz, about 33 mol. per cent plus A; of the Z102 content to 55 mol. per cent of Ti02, up to about 15 mol. per cent of A1203 and at most equal to the ZnO content. replacing a corresponding amount of the TiO2 and a fluxing agent.

GERARD HEINRICH JONKER.

References Cited in the file of this patent n FOREIGN PATENTS Number Country Date France 1937 

1. A CAPACITOR DIELECTRIC CONSISTING OF A SINTERED MASS OF ABOUT 1 TO 40 MOL. PERCENT OF ZNO, MORE THAN 10 MOL. PER CENT OF ZRO2, AND ABOUT 33 1/3 MOL, PER CENT PLUS 1/3 OF THE ZROZ CONTENT TO 55 MOL. PER CENT OF TIO2, SAID PRODUCT LIVING 